Device fob impressing sound-waves on diaphragms



C. G. HENSLEY. DEVICE FOR IHPRESSING SOUND WAVES 0N DIAPHRAGMSJ APPLICATION FILED JAN. 31,1918. RENEWED APR. 5,192!- Patented Nov. 15, 1921.

flz/rerawf' UNITED STATES? PATENT- OFFICE amass e. smsmz, 0F nnooxmm, NEWlYOBK. l

nnvrcn For.) nrrnnssnifo scone-waves on nmrnnaems.

1,397,04 To all whom it may concern: l Be it known that 1-, CH'A'RIES G. HnNsLnr;

a citizen of -the United States, and a 'resi dent of the borough of Brooklyn; 'city and State of New York, --have"invente d certa-in new and useful 1 Improvements in Devices for Impressin' Sound-Waves] ion "-Dia phragms, of win h the following is a' -sp'eci- 08.131011 1 -'.""-"5- 'ii' The present invention relates to a device for' impressing sound waves-on a diaphra m? The device adapted *for use ja record'er' for making phonographrecords,-asa micro? phone or telephone transmitte er fqr a other purpose where sound waves-"are i pressed on a diaphragm} In'the drawing ave shown a 'device provided with a lag phra "and a stylus lever for recording soung gvaves on a 'record" for use in phonog graphs'but it fis to be understood that the operation of my invention is practically the same regardless of whether'the' diaphragm operates a stylus lev'er'or creates 'iin'pulses in an electric circuit. v

My object is to remove all 'thedefects present in previous devices for collecting and impressing sound waves on 21. diaphragm.--

In all previous attempts to fc'ollect and impress sound waves ona diaphragm; so far as I am aware, some instrument such as a horn or concentrator having an open air space has been used to collect and concentrate the sound waves. Usually the collecting and concentrating" device has been 'in the nature of a horn or some such 'equ1valent means with an open air space and with a larger area at the open end where the sound waves enter and with a smaller area where the sound waves strike the diaphragm.

Such devices operate on principles almost contrary to the laws of acoustics and are therefore very inefficient. In recording sounds on phonograph records, for instance, it is necessary to place the speaker or artist very close to the receiving end of the horn in order to make what is now considered a loud record. This results in recording the sounds so that they reproduce in an unnatural way and in the case of a. singer for instance, the reproduction has the same effect as if one listened to the singer at a short distance from the artists mouth and v spasma n 0: Lett r at Patented Noy; 1-5, 1921. a ne -10a filed-'January 131', f1918,' sesame-214,629. renewed a -n s, liiZIfi-Siarhil m. 459,01 i

" as'one-seldom-liears a singer under such cir cfnnstances,- the effect does not seem natural-l If the artists are' placed farther away from" the ihorn'," even a a few-feet, the repro-- ductionl-is then unsatisfactory bec'ause'theg sounds make it appear as if the. artists were ve Mlistant from the recording instrument an much of the finer detail is lost.

' Anotherf diificulty with the present re- .corders is that-it is very difficult to get good reoqrding's'of a numberof voices or instru ments at' one' tlme because 1t is impossible a ree all-the singersor all the players near the re'cording instrument and the result isa; far away effect when the records are-played. p

:FUI l hBI'HIOI'B, while attempts have been made for years to secure louder recordings the record manufacturers have reached their limitin'this direction without obtaining the results they desired. It would seem to many that to make louder records it should only benecessary to use'larger recordin horns and have larger portions of the tote, sound waves come within the recording horn,-but such is not the case. Beyond certain very narrow limits it is impossible to-increase theamplitude ofrecording to produce loud records, byincre asing the size of the horn. Beyond certain limits the recordings are less pronounced as the size of the horn is increasedand the sounds are not'recordcd true but are distorted and the latter fact has led many to refer to the distorted sounds as extraneous sounds.

Another serious disadvantage in the present'systems of sound recording is, that in order to obtain sufliciently loud recordings it is necessary to use horns made of materials which lose much of the quality of the natural sounds. For instance, many of the record manufacturers use zinc or other metallic horns and these either impart a false or metallic quality to the recorded sounds or they fail to record the full true quality. Zinc is but slightly resonant, i. e, it is susceptible to very sli ht bending or vibration under the action 0 sound waves so that it really bends to the principal or main tones and to only some and not all of the overtones and for this reason many of the overtones are not recorded and much of the beauty of the music is lost. On the other hand, this very same characteristic causes the main or principal tones to be recorded louder than wonldbe the .ease if' a more resonantmaterial were used for the horn. Many wooden horns of various shapes have been 'used for making sound records b'ilt bwing" to theresouant nature oi wood it presented .othel. difiiculties in'therecording systems hereto fore used. In telephone practice many,"if not all, of the abovedifiicu ties are met with.

It isfiifiicult ;to,.proy id e a loud transmitter;

without multipiying all the defects of sound concentratioa-tmsuch an extent ,as to out weigh theadvantages of such an instrument.

One importantyreason-whydt has heretofore been?-impossible to acoomplish thede sired results is. because-the attempts have been contrary;:'to one-0f the gmainplaws of acoustics ,It'is well known-that a megaphone or horn ,.;when sound; waves. are 1 introduced into the smaller end, has the efl'ect of amplifying the. sound-waves and ofdireeting. them in some general direction. This prin-- ciple is riroperly-employedifi he reproduction of sounds. -In;the recording or transmission of sounds; however, arms been improperly used. When, in the recording or transmission of sounds the waves reach the largerjend of,the horn or collector, the large body ofjair, as well as the material of the horn, tend to reflectthe soundcgwaves why the same artist Will-record well at one.

time and not at another are not understood even by the most expert recorders and the difliculties are charged to weather conditions and such uncontrollable elements which, as a matter of fact, have very little to do with the results obtained. The defective results are due more to acoustical errors not heretofore understood.

The object of my invention is to overcome each and all of the defects of recording and transmitting instruments and to make possible the attainment of results which were heretofore impossible.

Instead of having a horn with a large body of air therein I provide a collector or concentrator having a comparatively small body of air and in this way I reduce the resonance of the device so that it is practically negligible. In reducing the body of air, however, I do not reduce the sensitin ncss or efliciency of the device but increase 'horns heretofore used. In

it, because I am able to secure the elfective energy of a large portion of the sound jvave device Ido not increase the size of the body of air therein inthe samedegree as in the i ct, one dimension of the air space may be kept ata minimum and for this reason there is a'linost nb limit to the-size the deviceinaypattain QIQlie effectiveness of the device, 2'. e., the recording or transmitting power, will increaseasithe, size of the dev ce glS, ii'icncased withoutabeiiig offset or counteracted by elements heretofore encountered. m i

,The sounds impressed onlfthe diaphragm are not distorted or rendered;unnatural -noi matter what the size obthefievice may be,- becauseof the compa ativ lrismell s n-space and slight resonance within the device." There 1 will be no ,confusionqof sounds even where sounds from severahvoieeswninstru; ments are ;;being simultaneously. recorded. or transmitted. Thesource ofithe sourrdmay be very close to the dev-i'ce anfisthere will nevertheless be no "blasting 'of the d. iaphragm. Louder recordings. mayv be had than with; any previous device. The record ings will be full and loud .even though the source of the sound be muclr farther away. from the instrument than in Iprior, ractiee. The artist instead of singing, tal ing, or playing. close tothe instrument may bea room length away and alLaudible sounds will nevertheless be recordeda w y The device' may be made of materials which will neither add false quality to the sounds nor subtract the naturalnquality. Sounds from any voice or instrumentmay be recorded with every natural overtone. In the preferred construction the device is made of wood preferably a soft, mellow wood such as pine or spruce. Although I am not the first to make a recorder or transmitter of wood I believe I am the first to obtain the desired results with this materiah Other advantages will; be madeapparent by the detailed description of one embodiment of my invention.

In the drawing forming part of this application,

Figure l. is an end elevation of theidevice looking at the end having the recording or transmitting diaphragm,

Fig. 2 is a sectional View, taken on the line Q- Q of Fig. 1, and

Fig. 3 is a sectional view, taken on the line of Fig. 2. V

In the drawing 1 indicates the diaphragm on which the sound Waves are to be irn pressed. In the illustration this is shown as a diaphragm to be used for making phonograph records. \Vhere the device is to he used as :1 telephone transmitter an ordinary microphone will bevzpositioned so that its. diaphragm occupies the same position as the diaphragm 1, and-as the adaptation will bereadily. understood by those skilled in the artl'ihave -iiot'shown a microphone in the dT flWiD ab i i The diaphragm 1 is shown as placed in a rabbet 2 of a member 3, and clamped between the-washers .4 and-5 by mean's'of a metal-ring 6 which is secured to the member 3; 3.851)? :ineans Q'f t-the, screws 7. In other words th'e diaphragm is fastened around its edge, preferably by means commonlynsed in the-art. i

s The stylus lever'or holder 8 may be of any approved form and ;the one shown herein has one end fastenedratfl to the center of the diaphragm.' The lever is fulcrumed at 10 to a;-bearing-jplate -1-1 secured to the member 3; and a suitable recording. stylus 12'is held in the:.socketfl'3ononeendjof the lever. The vibrations'of the;stylus leveriare'traced on the-record I l-revolving beneath it. beunders'tood. that the device isadapted for use with any-formof stylus lever known in the art, the one herein being shown only-by way of-example. f

' The diaphragm lie the recording or transmitting diaphragm on which the sound wavesare tOwhB impressed." It may correspond inisizevwith therecording diaphragms now-generally used but where my invention is used in its entirety the=diaphragm 1 may be largerthanthose 'now used without encountering the disadvantages heretofore met 7' i a i V Y The numeral-3pindicates the outer member of the concentrator, and while this may be varied in shape itis desirable that its interior be of decreasing area from its forward end 15 toward the end having the diaphragm 1. I find the most satisfactory results are attained when the bore 16 of the member 3 has a constant taper from its forward end to the end having the diaphragm 1. It is preferable that the angle of taper be long as the length in proportion to the diameter of the larger end of the bore affects the sensitiveness of the instrument.

In present practice the horn corresponding to the member 3 is usually hollow, so that it contains a large body of air which makes the horn act as a resonator, rather than as a concentrator of the sound waves. In the present case the body of air is reduced so that it has no appreciable resonance.

In the preferred structure I provide an inner member which I shall here refer to as a core and which is designated as 17. This core is positioned within the member 3 and it is held in spaced relation to the latter to form an air space of the shape of a hollow cone. The sleeves 18 inserted between the core 17 and the inner surface of the member It will 3 hold the core separated from the latter, while screws 19 passing through the member 3, the sleeves 18 and into the core, secure the latter against displacements. I have shown four such sleeves and screwsnear each end of the core but the number and positions of the spacing and securing means are not important and any other device may be used for the purpose.

jThe core 17 ispreferably ofthe general shape of a frustum of a oone..: In the form herein shown the'core has a broad, flat'for ward surface 20, from which thecore tapers gradually smaller to its rear end and the latter is shown as curved at 21 sovthat the space 22 between the core and diaphragm graduallydecreases from the outer portion of the diaphragm toward the center thereof; In the preferred construction-the outertsur face of the core is parallel with the-inner surface of the member 3 for the greater ipora tion of the length so that there is formed between the core and member 3 an air space 23 in the form of a hollow cone and this spacemerges into the space 22between the smaller end of the core'and the diaphragm 1. Some part of the inclosing means is' made of very resonant material and preferably this comprises a diaphragm or equivalent means disposed across the large end of the member 3. I haveshown washers 24.,atthe large or forward'end of the member 3 and between these there is clamped a diaphragm 25 the parts being secured in place by-a ring 26 which is secured by screws 27 extending into the end of the member 3. .The diaphragm 25 closes the larger and of the member 8 and it is separated from theforward end of the core to form an air space 28 which communicates, around the edge of the core with the air spam-:23. Preferably, the diaphragm 25 is parallel with the front surface 20 of the core.

In using the device to impress sound waves on the diaphragm 1, whether the latter be used for recording the waves on a phonograph record or for any other purpose, the larger end will be directed toward the source of the sound waves. The sound waves will strike the diaphragm 25 and this will be Set into vibration thereby. The vibrations set up in the diaphragm 25 will cause the air in the spaces 28, 23, 22 to be vibrated and the air in turn will set up corresponding vibrations in the diaphragm 1. Each time the diaphragm 25 bends inwardly or toward the core it causes the diaphragm 1 to bend outwardly in the center and, vice, versa, when the diaphragm 25 bends away from the core it causes the diaphragm 1 to bend inwardly at the center.

The sensitiveness of the device or the extent to which the diaphragm 1 is flexed in response to a given sound wave depends to a great extent upon the superficial area of the large diaphragm 25. To some extent it depends upon the distance the diaphragm 25 is from the source of the sound; but in the present case sounds originating somerdistancefrom the instrument have a greater effect on-the diaphragm 1- than in instruments heretofore used. This is due to the factthat the resonanceof the device,.i. e. the tendency to reflect or throwr'out5' thesound waves isless by reason of the small air space within the concentrator. With'a, large diaphragm 25'and a space at 28 of large area the sensitiveness ofthe device is justas pronounced, and in fact, more so, than if the wholeiinterior of the member 3 were merely filledwith air. But while obtaining the effect of a largearea, thusutiliz in'g a large portion ofthe energy of thesdund Waves fronrthe source of thesound, nevertheless, the "present device eliminatesthe resonant etfect'of the large body-of airs believe that the less -.air there is i'n the'1hember'3 the less the wall of this member tends reflect the sound waves back. toward their source or away from the diaphragm 1..

In the complete embodiment of my invention the entire air space in the member 3, i. e., the spaces 28, 23 and 22 ,are'all sealedor entirely closed, so that any bending of the large diaphragm 25 will more completely compress therair in the device and this will more perfectly transmitthe energy to the diaphragm 1. smaller the body of air contained inthe' device the stronger it is compressed by the diaphragm 25 and therefore," the more completely the action is transmitted to the diaphragm 1-.

It will be noted that the area of the air space 23 decreases from the position near the diaphragm 25 toward the diaphragm 1 and" this causes the rather short vibrations of the diaphragm 25 to be translated into movements of great amplitude in the diaphragm 1.

In the preferred construction shown herein the air waves approach the diaphragm 1 around the outer portion or near the edge and they then converge toward thecenter. A compression forces the diaphragm 1 to bend outwardly at the center, the compression being absorbed or lost by this bending action. Conversely. a rarefaction causes the diaphragm l to bend inwardly at the center and it is lost or absorbed by this bending action. A given wave. once it has moved the diaphragm l ceases and it does not recross the diaphragm as might be the case if the waves were applied to the diaphrugm as in Formcr practice.

lo the preferred construction the core 17 and member 3 are made of wood. prel'eraltvly pine spruce or some such wood which os sesscs the cliaruclcrislic of htuuling to all tone waves. \Vith a device made of such To a certain extent, the

material non e'of gthe quality of the sound Waves is' lost in-thefconcentrator, sothat not only ithe:principal tones'but all the overtonesidrrharmonicsare also impressed on the diaphragm il-s -But, asi 'distinguished from former devices, the recordingsavilhbe loud notwithstanding that; the device i is made of :woo'd,.z because :the resonance 1 or reflectingcharacteristic :isreduced 1 The. icharacteristic" blasting of Efo'rmer desiiees is eliminated; =and I attribute this toi a great extent to the comparatively. low

resonanceofithe device; l i

The best results are obtained if the core ll'is 'made solid, or,- ifr'partially hollow; then that wall) shou11i:be=-thick i in order that: the core ishall unot' be 1 resonant to. the sounds acting .o'nlthe device. It uis' advantageous also; to: have lilac):Wall of the member 3 thick, fortheisan'l mama-mm .J

vThe .presenti device mayubeimarlefvais darge as BBSLUBdC'" rflhe'i-lengthk may be extended andtlie diaphragm 25iincreasd so that'it shall mama ffe'eerin diameter without hav im'gLthe counteracting disadvantages 0f pres vieu s' devicessv Lhavefou-ndlthat the thinner the diaphragm 25 in proportion to its area the more sensitive the deviceiis to sound waves I? have des ribed my device above as a recorderyor'z'transmitter in which: sound waves from= a =sonrce of-sound action a larger diaphragm so that the" waves are ultimately impressed onthesmaller or record ing diaphragmi' l; desire to be protected, however, in all uses to which the device is adapted, andcthfielaims; herein are. intended to cover niy intention even: though it be used iniother'whyse'eFor instance; the device'rma'y be used in'the-reverse way to that described: aboveflin whichcase it may be employed as a telephone receiver or as a phonographireproducer.

The stylus lever 8. may be vibrated by means of anordin ary phonograph record so that the sound? waves previously recorded on a record are impressed on the diaphragm 1 the same as the'waves are impressed or reproduced on the diaphragms of the ordinary reproducer, or, a telephone receivermay be positioned so that its diaphragm occupies the-position occupied by the diaphragm 1. If thediaphragm 1, or, in the latter case. the receiver diaphragm be vibrated to reproduce sounds the waves created at-the smaller end of the present device will traverse the spaces. 22, 23 and 28 in the reverse direction to their movement when the device is used as a recorder: The waves will act on the diaphragm 25 and the movement of the latter will cause pulsations of the air at its outer s de and reproduce in the room the sounds represented by th groove of the phonograph record or the electrical impulses received over the electric circuit.

wThe di'a hragmr 25 willu-move Z in unison with .the diaphragm land eveniif t-he extnt of its movement noti' as great as the 'diaphragm 1 nevertheless, owing'to-fits greater superficiah :area it: Millqdisplacei a comparativelyxlargesljody ofz airteai'idiitlris-lwill have the effect*of=amplifying5th'sound. The device will amplify the sound waves so that they are reproduced as loud as or louder thanif the waves were created in the ordinaryireproducer and sent through a tone arm and horn as is now done. But the re roduction will be free of that unnatural be low efi'ect always present in machines which use the hollowhorn for amplifying. The device sounds as if the waves were actually reproduced in the first instance at the diaphragm 25, even if as a matter of fact, they are not so reproduced. Owing to the small air space in the device as compared with amplifying horns now used the unnatural roundness or overfullness is eliminated. This also makes it possible to provide a very large amplifier for creating very intense sound waves and without the increasing hollowness which always results when iiiciiieasing the size of the hollow horn am- 1 er. P In describing details of one embodiment of my invention and in referring to certain preferred proportions or materials I do not wish to be understood as limitin myself thereto except in such of the ollowing claims as positively include such limitations.

Having described my invention, what I claim is:

1. A device of the class described comprising a smaller diaphragm. a larger diaphragm, and spaced members forming a tapering fluid space of annular cross section and with which members said diaphragms are so associated that the vibrations of one of said diaphragms are transmitted to the other of said diaphragms through the fluid in said space.

2. A device of the class described comprising a smaller diaphragm, a larger diaphragm, and spaced members forming a tapering fluid s ace of annular cross section and of gradua y decreasing area and with which members said diaphragms are so as sociated that the vibrations of one of said diaphragms are transmitted to the other of said diaphragnis through the fluid in said space.

3. A device of the class described comprising an outer member having a tapering bore, a core in said member and spaced therefrom to form a fluid space around the core and diaphragms arranged in spaced relation to said core and adapted to transmit sound vibrations from one to the other thereof through the fluid in said space around said COI'G.

t. A device of the class described comprising an outerim ember having a" tapered bore, a tapered core in saidiouter member and Spaced therefrom to form a-fluid space of radually decreasing area around .the core, a arger and. a smaller. diaphragm arranged in spaced relatiom tdgsaid. core 2' and adapted to tramsm itxsbiind' vibrations from-one to the other thereof through the fluid in said space and around said core.

5. A device of the class described comprising an outer member, a tapered core therein and spaced therefrom to form a fluid space of annular cross section, a smaller diaphragm, arranged in spaced relation to the smaller end of said core and a larger diahragm arranged in spaced relation to the arger end of said core, said diaphragm being adapted to transmit sound vibrations from one to the other through the fluid in said spaces.

6. A device of the class described comprising an outer member, a tapered core therein and Spaced therefrom to form a fluid space of annular cross section, a smaller diaphragm, arranged angularly to the axis of said core and spaced from the smaller end thereof and a larger diaphragm arranged at an angle to the axis of the core and in spaced relation to the larger end thereof, said diaphragms being adapted to transmit sound vibrations from one to the other through the fluid in said spaces.

7. A device of the class described comprising an outer member having a tapered bore, a tapered core therein and spaced therefrom to form a fluid space of annular cross section, a smaller diaphragm, arranged in spaced relation to the smaller end of said core and a larger diaphragm arranged substantially parallel and in spaced relation to the larger end of said core, said diaphragms being adapted to transmit sound vibrations from one to the other through the fluid in said spaces.

8. A device of the class described comprising an outer member made of wood, an inner core made of wood and spaced from said outer member to form a fluid space between them of annular cross section and of gradually decreasing area, a smaller diaphragm spaced from the smaller end of said core and a larger diaphragm spaced from the larger end of said core, said diaphragms being adapted to transmit sound vibrations from one to the other through the fluid in said spaces.

9. A. device of the class described, comprising a smaller diaphragm on Which the sound waves are to be impressed, means associated therewith for recording sound waves on a phonograph record, a larger diaphragm adapted to be acted upon by sound waves and means forming a fluid space and with which said diaphragms ure so associated that the vibrations of said larger diaphragm will be transmitted to said smaller diaphragm through the fluid in-said space. Y

10.A devised the class described comprising an outer member made, of wood and :6 having-hampered !b0re ,-a1c0re;made of wood and-anrzingd'inrsaid first member to form afiuid space around the core and diaphragms arranged in spaced relation tosaid core and adapted to transmit sound 'Weves' from one to the other through: the fluid insaid Space 10 around said core.

Signed at theeity, .countywand-State of New York this 23rd; day of January, 1918. Q ,;CHA'RLES G'.HENSLEY;-'J 

